Simple Mendelian inheritance of the reiterated ribosomal DNA of yeast.

Abstract

A diploid strain of yeast (Saccharomyces cerevisiae) was heterozygous for 2 forms of the highly repetitious ribosomal DNA. These forms could be distinguished by the pattern of fragments produced after digestion with the site-specific restriction endonuclease EcoRI. The mode of inheritance of ribosomal DNA was determined by tetrad analysis. Of 14 tetrads analyzed, 12 clearly showed the ribosomal DNA forms segregating as a single Mendelian unit. The simplest interpretation of this result is that all of the approximately 100 copies of the ribosomal DNA genes of the yeast cell are located on 1 chromosome and that meiotic recombination within these genes is suppressed. Two of the 14 tetrads showed the segregation patterns expected as the result of mitotic recombination within the ribosomal DNA. [The DNA probe was prepared from an Escherichia coli strain].